Rheumatoid arthritis (RA) is the most common inflammatory arthritis affecting 1-2 percent of the adult population in the US and increases in prevalence into the 7th decade. Osteoporosis also affects older adults and its risk is increased in patients with RA. Except for several relatively small trials in glucocorticoid induced osteoporosis, relatively few patients with RA have been enrolled in clinical trials of osteoporosis treatment. The combination of RA and osteoporosis is especially problematic because of the substantial disability and pain associated with both conditions. Because the inflammatory milieu of RA may alter the effects of osteoporosis treatments, there is a pressing need to study such treatments in patients with RA. As well, it is possible that some anabolic bone agents and potent bisphosphonates may treat the osteoporosis and articular erosions, the localized bone disease so common and disabling in RA. This grant will assess the relationship between articular bone erosions and bone mineral density. We will recruit patients from a large single-center cohort study of RA, the Brigham Rheumatoid Arthritis Sequential Study (BRASS), with approximately 850 patients currently enrolled and a goal enrollment at 1000. Three hundred postmenopausal women from this cohort will be recruited for a standardized dual-energy x-ray absorptiometry (DXA) examination of the spine and hip to assess bone mineral density (BMD). As well, patients will have hand and wrist x-rays scored using detailed methods for grading articular bone disease of RA. Stratified and multivariable models will control for markers of RA disease severity, demographic, anthropometric, medication, and other clinical variables that may affect the relationship between local bone disease and general osteoporosis. We hypothesize that articular erosions and BMD will be correlated but their association will be significantly modified by functional status and cumulative glucocorticoid dosage. This epidemiologic data will inform future trials of osteoporosis treatments among patients with RA. As well, the study cohort will comprise one of the largest RA registries with an explicit plan to examine osteoporosis.